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Redox State and Transition Metal Concentration Effects on Microstructure of Simulated Simplified Glasses for Waste Immobilization

Published online by Cambridge University Press:  15 February 2011

C.-W. Kim ,
I. S. Muller ,
A. C. Buechele ,
I. L. Pegg  and
P. B. Macedo
C.-W. Kim
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington. D.C. 20064
I. S. Muller
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington. D.C. 20064
A. C. Buechele
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington. D.C. 20064
I. L. Pegg
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington. D.C. 20064
P. B. Macedo
Affiliation:
Vitreous State Laboratory, The Catholic University of America, Washington. D.C. 20064
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Abstract

Chromium, iron, and nickel are present in many waste-streams from DOE sites. This study considers a simplified lime-aluminosilicate glass system, similar to one proposed for high temperature (1250–1450°C) vitrification of soil and wastes from DOE sites, in which concentrations of Cr, Fe. and Ni are being varied and different redox states induced for selected melting conditions. The solubilities of Cr 2O3 and NiO in the simplified system are determined at 1350°C, 1400°C, and 1450°C. The enthalpies of solution calculated from the solubility data for Cr2O3 and NiO are 12.2 and 15.2 kcal/mol, respectively. The iron redox ratio, Fe2+/Fetotal in selected glasses is determined by Mössbauer Spectroscopy and related to changes in microstructure. The crystallization of eskolaite (Cr2O3) seems to be favored at intermediate states of reduction (Fe2+/Fetotal ≈0.8) in Cr-containing glass at near the solubility limit. Pseudoternary diagrams are plotted for melts in air at 1450°C in which Fe2O3 + SiO2 + X (X = NiO or Cr2O33) is held constant. Time-Temperature-Transformation (TTT) curves are plotted using data from heat treatment studies. Liquidus temperatures of base, 1.5 wt% Cr2O3 glass and 8 wt% NiO, 7 wt% Fe2O3 glass are found to be 1150°C, 1175°C, and 1175°C, respectively.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 412: Symposium V – Scientific Basis for Nuclear Waste Management XIX , 1995 , 149
Copyright
Copyright © Materials Research Society 1996

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References

1. Lutze, W. and Ewing, R.C., eds., Radioactive Waste Forms for the Future, (Elsevier Science Publishers, North Holland, 1988), pp. 3–4.Google Scholar
2. Muller, I.S., Ruller, J., and Pegg, I.L., Vitrification Treatability Studies for MMES/Oak Ridge Wastes, Monthly Progress Report for March, (1995).Google Scholar
3. Muller, I.S., Gan, H., Lai, S. -T., Buechele, A.C., and Pegg, I.L., Development of a Vitrification Compositional Envelope to Support Complex-Wide Application of MAWS Technology, final report submitted to Argonne National Laboratory, (1995).Google Scholar